This invention relates in general to, the ability to establish a plurality of organized voids in a material, and also to load bearing structures and structures that provide an enhanced trade-off between the stress that can be safely carried in relation to the amount of material required for the structure.
Generally, voids have been created in materials using a number of existing foaming techniques. These foaming techniques produce materials having voids which are unorganized; i.e., the voids are randomly positioned as well as randomly placed. Moreover, a number of the voids in these materials are not enclosed—they are interconnected with adjacent voids.
Accordingly, existing processes cannot produce materials having enclosed voids and/or voids in a truly organized position within a material. Current techniques will also not allow voids to be created to an exact predetermined size and shape which are substantially self-enclosed.
Having voids which are organized non-interconnected voids is especially important in stress steering materials. Stress steering materials allow for forces placed on a structure to be resolved largely into compressive forces.
Such stress steering materials having symmetrically arranged voids have been developed which resolve a substantial majority of the stresses placed on the material into compressive stress using a novel structure containing voids. Such novel structures are disclosed in U.S. Pat. Nos. 5,615,528, 5,660,003, and 5,816,009, the disclosures of which are incorporated herein by reference (each patent being owned in common with the present application). Each of these disclosures describes the use of a plurality of uniform, symmetrically arrayed voids throughout the base material which results in a material structure that resolves the forces imposed thereon largely into compressive rather than tensile stress.
Research by NASA, and other respected scientific organizations, has determined that the more nearly uniform the voids and the more nearly symmetrical the arrangement of voids in a material, the greater the effective tensile strength of the material. Consequently, makers of foamed materials, and other materials in which porosity is a factor, have long sought a commercial method for positioning pores, or voids, of a predetermined size(s) in predetermined locations in a material to give the material a precise, three-dimensional morphology in order to optimize its effective tensile strength.
However, incorporating these voids in a three-dimensional symmetrical arrangement in materials is at best an arduous and costly task using conventional manufacturing techniques. Indeed, this is not yet possible with known material foaming techniques. Hence, the widespread use and acceptance of porous materials, including the stress steering materials disclosed in the above-identified patents, have been hampered due to the difficulties of incorporating the essential voids in materials.
Accordingly, there exists a need for a material, process, and/or system that will allow for easy manufacture of materials with predetermined morphologies that incorporate voids, including the patented stress steering materials.